Recently, a brushless DC motor employing permanent magnets has become widely used for driving a fan of a ventilator. FIG. 23 shows a circuit diagram of a conventional brushless DC motor coupled directly to an AC source to be used for driving a fan. The circuit uses the two-phase half-wave driving method and comprises the following elements:                rectifier 101 for rectifying the commercial AC power;        smoothing large capacity aluminum electrolytic capacitor 109;        two-phase stator coils 103, 104 for driving magnet rotor 105; and        controller 102 for controlling the power to the stator coils, including switching elements 107, 108 and being mounted on printed circuit board 106. Stator coils 103, 104 are provided with a high voltage DC power source directly from rectifier 101, and controller 102 is provided with a low voltage reduced from the high voltage DC power source. The foregoing brushless DC motor driven by the two-phase half-wave driving method generates rather large noises and vibrations, and needs a smoothing capacitor of large capacity. The present invention aims to provide a brushless DC motor coupled directly to the AC source which overcomes those problems.        